The present disclosure relates generally to reciprocating saw tools and more particularly, to an improved reciprocating saw with a reinforced saw blade holder that is mounted to a slotted drive shaft.
In the insulating foam industry, installers spray an insulating, expanding foam into selected building wall areas, such as those areas between adjacent studs of the building framing. The sprayed foam expands and sets and extends past the faces of the wall studs. This excess foam must be trimmed by the installer in order for interior and exterior sheathing and SHEETROCK® drywall or wall board to be applied to the framing. The foam is commonly trimmed by a hot wire that is pulled along the stud faces by an installer, or with a thin-bladed saw, such as a coping saw. Both of these methods are difficult to employ and both require substantial labor, reducing the potential profit for the installer. Installers now use reciprocating saws in order to trim the sprayed foam more quickly and more efficiently.
In order to make the process of using a reciprocating saw to remove excess foam more efficient, I developed a modification for an existing reciprocating saw that converts an ordinary reciprocating saw into one with an offset blade holder and a second, exterior handle. In this modification, I provided an offset mounting head that includes a mounting block with a hollow bore that receives therein, the free end of the saw tool drive shaft. The offset mounting head permits the installer to place the saw blade into closer contact with the faces of the framing studs to achieve a better trim of the insulating foam.
However, the free end of the drive shaft of the saw tool has a central slot that receives the attachment end of the saw blade, and the saw blade is secured to the shaft by means of a set screw or the like that extends through one of the drive shaft halves flanking the slot, into the drive shaft slot and into contact with an opposing surface of the saw blade. Although in my prior offset saw, the saw blade was no longer held in the drive shaft slot but mounted instead to a mounting block of the offset assembly, the drive shaft slot remained slotted as the replacement of it would make the resulting saw commercially unfeasible. The slotted drive shaft was used and the mounting block was slipped over the drive and a set screw was used to secure the mounting block to the drive shaft. The set screw extended through one of the drive shaft halves and into the slot.
This drive shaft slot creates a natural area in the drive shaft for stress risers to occur, i.e., areas of concentrated stress and this may result in one or both of the drive shaft halves deflecting under impact loading, or worse, breaking. Impact forces that occur when the end of the saw blade contacts a stud or sheathing during operation are transferred through the saw blade directly to the drive shaft to cause this stress. A need therefore exists for an offset saw blade mounting assembly used with a reciprocating saw in which the manner of mounting the saw blade is stronger and more resistant to stresses which may induce drive shaft failures.
The present disclosure is therefore directed to an improved offset saw blade mounting assembly for a reciprocating saw with a means for reinforcing the slotted drive shaft.